Fluid flow control valves are known which use flexible, resilient diaphragms for sealing against a valve seat. The diaphragm flexes away from the valve seat to open the valve and allow fluid to flow between the valve inlet and outlet. Typically, an annular peripheral rim portion of the diaphragm is clamped between two mating portions of the valve to support the diaphragm in the valve. U.S. Pat. No. 4,505,450 to Saarem discloses such a valve in which the rim portion of the diaphragm is clamped between the valve body and a separable cap therefor.
In most valves of this type, including the Saarem valve, the annular rim portion of the diaphragm is tightly compressed to prevent leakage between the diaphragm and the mating valve portions. Saarem uses an open-ended nut which can be screwed down to force the cap against the valve body and thereby compress the rim portion. Other known valves use a plurality of spaced, threaded bolts which extend through the mating valve portions. These bolts can be sufficiently tightened using a wrench to compress the annular rim portion of the diaphragm.
The resilient diaphragms previously used in such valves are typically molded in one-piece from an elastomeric material such as rubber. As the diaphragm diameters expand for larger sized valves, e.g. diaphragms having a 5 inch diameter, the size of the peripheral rim portion needed for adequate sealing often also correspondingly increases. It is difficult to properly mold such larger diaphragms without having deformities or other manufacturing imperfections that occur in the peripheral rim portion. Accordingly, there is a high scrap rate for such diaphragms, which increases the cost of manufacturing such valves.